Heretofore, 5-fluorouracil and various derivatives thereof have been known as antitumor agents. However, all of these derivatives do not always show the effectiveness expected and it has been generally recognized that they cause immunosuppression when used. In addition, some of 5-fluorouracil derivatives are highly toxic and might have side effects.
Consequently, the present invention aims to provide compounds which have no defect shown by conventional 5-fluorouracil derivatives, have less toxicity, can be dissolved in an oily material in a stable state so that they can be easily absorbed in body and are useful as cancerocidal agents.